Wound Grafts

Indications

Indications of skin grafting include deep second—or third-degree burns, traumas, and non-healing or large wounds that do not close via primary or secondary intention. Patients who may benefit from skin grafts include burn patients, patients with non-healing wounds, such as diabetic foot wounds, or patients who have had to undergo extensive excision, such as necrotizing fasciitis.

Contraindications

There are few contraindications to wound grafts except for a few, such as an infected wound bed and an under-resuscitated patient.

Preparation

The following are some necessary prerequisites needed to carry out the procedure of wound grafting successfully:

• Watson knife, Goulian blade
• scalpel 
• electrocautery 
• dermatome 
• mineral oil 
• skin mesher
• suture or staples

An appropriate team includes a well-trained surgeon, an anesthesiologist, a scrub tech, and a scrub nurse. Preparation of the wound bed is essential to a successful procedure. Early excision and debridement to healthy tissue are vital to the graft's healing. The standard of care for successful grafting is a 95% graft take. Removing eschar and necrotic tissue promptly lowers the risk of developing a wound infection. This is essential to preventing the loss of the graft. Early excision has also been proven to decrease the number of contractures, scarring, and skin tightness, and patients often are rehabilitated faster.[10][11] The eschar is removed in layers until healthy tissue is identified by diffuse punctate bleeding with a Watson knife or Goulian blade. This is known as tangential excision. Fascial excision allows for faster resection and provides a plane ready for grafting but can lead to subpar cosmetic results. Wounds over joints need early excision and grafting to help prevent excessive contracture.[12][1][13] Before placing the graft, all granulation tissue should be excised as it can have a significant bacterial burden and prevent adherence to the graft. Skin margins should be freshened to expose healthy dermis. Hemostasis must be ensured to prevent the formation of a hematoma, failing the graft.[1]

Technique or Treatment

Full-thickness skin grafts include both the epidermis and the dermis. The donor site selection is carefully considered for optimal cosmetic outcome and control of discomfort. Cosmetic outcome is based on desired pigmentation, texture, and skin thickness.[2] These skin grafts minimize the degree of contracture across joints and on the face and fingers.[14][2] Full-thickness grafts are chosen from the flank, groin, hypothenar eminence, pre- and post-auricular areas, or the forearm.

• The skin is shaved, and the tumescent is injected into the tissue below the intended donor site.
• The skin is then gently harvested using a scalpel, customizing the shape to that of the area to be grafted. Sharp dissection is preferred as electrocautery can damage the donor graft very easily.
• The graft removes some of the subcutaneous tissue. It is then taken to the back table and “defatted” to remove the excess tissue. The donor site is then closed primarily.
• When placing the full-thickness skin graft, it is sutured along the edges using rapidly dissolving sutures. Many surgeons use quilting sutures to help hold the graft in place, preventing both shear and empty space in which a hematoma or seroma could develop. Larger grafts (>3 cm diameter - Stephenson) risk failure because the surface area is too large for adequate imbibition.

STSGs are the most common type of wound graft placed. They are ideal because smaller amounts of harvested skin can cover a larger area. The dermis and epidermis from the donor site also heal quickly (10-14 days), and that location can be used as a donor site again if necessary. The ideal donor site is the anterolateral thigh because it is easily accessed on the supine patient, it is easy to use the dermatome in this location, and the dressings required are in an easily accessible location.[15] STSGs are generally meshed to increase coverage when limited donor skin is available. This is useful for decreasing the amount of skin harvested. Still, the interstices also allow for the egress of serum and blood buildup, minimizing the risk of losing the graft because it maintains contact with the underlying wound. The most common ratios utilized in meshing are 1:1 to 3:1. Increasing this to 4:1 or higher can be done, but there is an increased risk of the graft not being taken because the distance between the interstices is too large for the skin to heal.[16][14]. When placed on the body surface to be covered, the graft's orientation can affect the amount of coverage available based on the meshing pattern.[17]

Sheet grafts are STSGs that are unmeshed. The largest disadvantage of STSGs is the cosmetic outcome. The meshing is scarred into place at the wound site. They also have increased rates of contracture during healing. Sheet grafts are used in areas greater than 3 cm on the face and hands to reduce contracture and improve cosmetic outcomes. If possible, they are also used in areas more commonly exposed, such as the forearms and legs. The risks of seroma and hematoma buildup resulting in graft loss are similar to those associated with full-thickness grafts, so they must be monitored closely.[1]

• Infiltrate subcutaneous tissue with tumescent infiltrate.
• Ensure the dermatome is at the correct height for the desired thickness. This can be as thin as 1/1000 of an inch, but the most common thickness is between 8/1000 and 12/1000. This can be easily checked with a #10 scalpel blade. If the blade falls into the space between the dermatome and the dermatome blade, the harvested skin will likely be too thick. The scalpel blade should fit into space easily and then become snug as the scalpel blade thickens. The appropriate thickness must be checked every time, even if the settings are the same.
• The area to be harvested is covered in mineral oil to decrease resistance. Tension is applied to the donor site to make it as even and flat as possible. The dermatome is introduced at a 45-degree angle and advanced while placing downward pressure. It is essential to place appropriate pressure to keep the dermatome in the dermis. Too much pressure results in a skin graft that is too thick, and the donor site needs more time to heal or may even require primary closure if a full-thickness graft is taken. Too little pressure results in a skin graft that is too thin, uneven, and irregular. Once the desired length is obtained, the dermatome is lifted off the surface, generally amputating the graft from the adjacent skin left in place. If it does not amputate, it can be severed with a scalpel. The donor site is then covered with a 1:1000 epinephrine and a normal saline pad for hemostasis.
• If the graft is to mesh, it is taken to the back table and placed in the meshes at the desired ratio.
• Once meshed, the STSG is placed on the wound, with the dermis side contacting the wound bed. It is then either sutured or stapled into place to reduce shearing and improve contact with the wound. Fibrin sealants can also be secured, but these are often used in combination with staples and sutures.

Dressings

• Graft site
• The graft must be immobilized to prevent shear injury to the healing areas. Shearing results in failure of neovascularization and graft death. This is especially important with full-thickness grafts and sheet grafts.
• Negative pressure wound therapy is an ideal dressing choice because it removes all excessive fluid from under the graft while keeping it in place. This minimizes the risks of shearing. This is the preferred dressing method for many surgeons to protect the skin graft and has been demonstrated to be superior to bolstered dressings.[18][19]
• If negative pressure wound therapy is not available, bolstered dressings can be placed and tied or sutured into place to ensure that the underlying graft does not move. The bolster is generally an absorbent gauze to assist with the egress of exudate.

• Donor site
• Donor site dressing options are numerous and often surgeon-dependent. A commonly used dressing is vaseline gauze. Using nonadherent dressings that won't pull off the healing skin when changed is important. The dressing is usually changed around postoperative day 5.

Complications

Failure of the graft can occur due to fluid build-up under the graft, infection, shearing, excessive tension, or poor vascularity of the wound bed. These complications can generally be avoided if appropriate wound bed preparation is performed along with meticulous hemostasis. The graft is further protected by securing it in place and by the dressings. Care must be taken along each step to provide the graft with the best chance of survival. Long-term contracture and scarring can result. Contracture over joints can be improved by early mobilization, but this must be carefully balanced to avoid damage to the underlying grafts.[13]

Clinical Significance

Skin grafts can be a life-altering procedure for patients with large wounds that would otherwise be unable to heal. Cosmesis is often determined by timely wound debridement and treatment, often at specialized centers, if the wounds are large enough. All teams must work together so that wound debridement and grafting occur promptly and patients have optimal outcomes. Patients with extensive injuries or burns who do not have sufficient skin available for grafting may be appropriate candidates for skin substitutes. Reestablishing skin continuity is essential to preventing infections, reducing insensible fluid losses, and providing patients with an increased quality of life.

Enhancing Healthcare Team Outcomes

Communication between the wound care specialist, the surgeon, and the care team is necessary to ensure that a proper wound bed is prepared and that no infection exists in the wound bed. The care team is essential to this process because they change bandages daily and see the wounds. They are also responsible for the patient's care after the graft when it is most fragile and must be protected.